Solid state electro-optical devices on a semi-insulating substrate

ABSTRACT

Solid state electro-optical devices are formed on a semi-insulating substrate, with all contacts of each device being on the same side of the substrate. These devices include two types of lasers, one operating on current crowding effect and the other by lateral diffusions. Either type laser is integratable with an electronic device e.g. a Gunn oscillator or an FET on the common semi-insulating substrate to form a complex monolithic electro-optical device.

ORIGIN OF THE INVENTION

The Government has rights in this invention pursuant to Contract No.N00014-74-C-0322 awarded by the Department of the Navy and pursuant toGrant No. ENG 76-04927 awarded by the National Science Foundation.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to optical devices and, moreparticularly, to optical devices and to monolithic opto-electroniccircuits on a semi-insulating substrate.

2. Description of the Prior Art

In recent years a significant amount of research has been directed todevelop various devices, utilizing semiconductor materials. Among thesedevices are optical devices and electronic devices. With modern chiptechnology very thin layers of semiconductor materials can be grown ordeposited on a substrate to produce very small devices. For example,with advances in GaAs device technology heterostructures of GaAs andGaAlAs have been developed to fabricate lasers. Also, due to the highelectron mobility in N-type GaAs high speed GaAs electronic devices,such as Gunn oscillators and FET's have been produced. Since opticaldevices, such as a laser, and electronic devices can be used to form acomplex optical circuit, it is highly desirable to be able to integrateall the devices to form a single chip, yet provide the electricalinsulation of the devices from on another for proper circuit operation.To date, such complex monolithic integration has not been possible forthe following basic reasons. All known GaAs type lasers are fabricatedon a conductive GaAs substrate. Likewise, the substrate of known GaAselectronic devices is electrically conductive. Due to such electricalconduction the integration of such devices into a complex monolithicoptical circuit i.e. one on a common substrate has not been possible,due to the need to electrically isolate the devices from one another.

OBJECTS AND SUMMARY OF THE INVENTION

It is a primary object of the present invention to provide a complexelectro optical monolithic circuit.

Another object of the present invention is to provide a complexmonolithic optical circuit in which a laser and an electronic device arefabricated on a common substrate, yet are electrically isolated from oneanother through the substrate.

A further object of the present invention is to provide new type lasers.

Yet, a further object of the invention is to provide a lasercharacterized by a new structure which lends itself to integrating thelaser with an electronic device on a common substrate.

These and other objects of the invention are achieved by fabricatingeach of the devices, which are to be integrated on a semi-insulatingsubstrate which is of GaAs, when the devices to be integrated arefabricated of GaAs. Since the invention will first be described inconnection with GaAs type devices, the substrate will be referred to asthe semi-insulating GaAs substrate, or simply the semi-insulatingsubstrate. The term semi-insulating is assumed to mean semi-insulatingelectrical properties with a resistivity of not less than about 10⁷ohm-cm. The integration of the various devices is achieved byfabricating them on the semi-insulating substrate in close proximity toone another to make the complex monolithic optical circuit as small asdesirable or practical. Since, the substrate is semi-insulating itprovides the required electrical insulation between the integrateddevices. Various embodiments of the invention will be describedhereafter.

Another object of the invention is achieved by providing a semiconductorheterostructure injection laser characterized by carrier crowding. Alateral diffusion laser with contacts on the same side of asemi-insulating substrate is also described.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a simplified block diagram of a laser integrated with anelectronic device on a semi-insulating substrate;

FIGS 2a and 2b are diagrams of one laser of the present invention;

FIGS. 3a, 3b, 4a, 4b, 5 and 6 are curves useful in describing theperformance of the laser shown in FIG. 2a;

FIG. 7 is an isometric view of a novel current crowding laser of thepresent invention;

FIGS. 8-11 are curves useful in explaining the laser shown in FIG. 7;

FIG. 12 is an isometric view of a different embodiment of the lasershown in FIG. 7;

FIG. 13 is a diagram of a current crowding laser integrated with a Gunndevice on a semi-insulating substrate;

FIG. 14 is a diagram of a lateral diffusion type laser integrated withan FET on a semi-insulating substrate; and

FIGS. 15 and 16 are diagrams of different lasers integrated withelectronic devices.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Attention is first directed to FIG. 1 which is a simplified diagramuseful in explaining some aspects of the present invention in connectionwith GaAs type devices. In accordance with the present invention acomplex monolithic optical circuit 10, shown consisting of a GaAs typelaser 12 and a GaAs electronic device 14 are formed on a commonsemi-insulating GaAs substrate 15. Grown on the semi-insulatingsubstrate is an active layer 16 of GaAs. This layer forms part of theelectronic device 14 and may or may not be one of the layers of thelaser, as will be explained herebelow. To provide circuit 10 with highspeed operating characteristics layer 16 is of the N type, which ischaracterized by high electron mobility. In operation, any current flowbetween the electron device 14 and the laser 12 takes place in GaAs (N)layer 16, while the semi-insulating substrate 15 provides the necessaryelectrical insulation between the laser 12 and the electron device 14.

Before describing several embodiments of complex monolithic opticalcircuits on the semi-insulating GaAs substrate 15, two different typesof lasers constructed on such a substrate will be described. Attentionis directed to FIG. 2a which is a cross sectional view of a GaAs-GaAlAsinjection laser 22 with a laterally diffused PN junction. The laserconsists of a three-epilayer double heterostructure on thesemi-insulating GaAs substrate 15. The three layers from the bottom areGaAlAs, GaAs and GaAlAs of the N type and are designated by 22a, 22b and22c, respectively. The P type region designated by 22d is obtained byselective Zn diffusion into the three layers. A P type contact 22e e.g.Au-Zn, is formed on the top surface of the P type region 22d, while an Ntype contact 22f e.g. Au-Ge, is formed on the surface of thenon-diffused portion of the GaAlAs top layer 22c.

Current flaws laterally across the PN junction in the GaAs layer 22bfrom the P type contact 22e to the N type contact 22f. Since GaAlAs hasa wider bandgap than that of GaAs, carriers are injected predominentlyacross the GaAs PN junction in the GaAs layer 22b. The effective area ofthe current injection is determined by the thickness of the GaAs layer22b. Very thin GaAs layers can be obtained by liquid phase epitaxy(LPE). Thus, low threshold can be and was achieved, with the laser ofthe present invention.

It is recognized that the technique of tranverse injection is not new.It is described in an article entitled "Tranverse-Junction-StripeGeometry Double Heterostructure Lasers with very Low Threshold Current"by Namizaki et al. J. Appl. Phys., vol. 45, pp. 2785-2786, June 1974.Another prior art article is entitled "Tranverse-Junction-Stripe Laserswith a GaAs p-n Hemojunction" by H. Namizake, IEEE J. Quantum Electron,Q E-11, vol. 7 (1975). The prior art structures suffer from currentleakage through the P GaAlAs-N junction due to the highly conductivesubstrate. Recently, such current leakage problems are claimed to havebeen eliminated by the structures described in "New Structures of GaAlAsLater-Injection Laser for Low-Threshold and Single-Mode Operation" bySusaki et al. IEEE J. Quantum Electronics vol. Q E-13, No. 8, pp.587-591, August 1977.

The structures described in the latter article also include a conductivesubstrate and each structure consists of five epilayers. In the laser22, shown in FIG. 2a, only three layers are included and the currentleakage is eliminated because the substrate 15 is semi-insulating. Thus,the laser on such a substrate is clearly more advantageous. It shouldalso be pointed out that in the prior art laser structures, the twocontacts are on opposite sides of the laser, one contact extending fromthe substrate. In the present invention both contacts are on the sameside of the substrate, and therefore simplify the connection of thelaser to other devices.

In one embodiment which was actually reduced to practice the laser 22was fabricated by LPE growth and selective Zn diffusion. The Ga_(1-X)Al_(X) As, GaAs, Ga_(1-X) Al_(X) As layers 22a-22c were grownsuccessively to thickness of 3, 0.03 and 2 μm respectively, with X˜0.45.These three layers, all of the N type, form the laser's doubleheterostructure in the vertical direction.

As shown in FIG. 2b a top layer of GaAs, designated 22g was grown onlayer 22c. It was used as a diffusion mask. It was found that Zndiffusion rate in GaAs is much slower than in Ga_(1-X) Al_(X) As and thehigher the Al content the faster the diffusion. By using GaAs layer 22gas the diffusion mask an extra step of depositing an ordinary mask sucha SiO₂ (doped with P) and Si₃ N₄ was eliminated. Because GaAs and GaAlAsare almost perfectly lattice matched, the GaAs mask layer 22g is morestable than the ordinary masks. The stress which exists at the interfacebetween the ordinary mask and the semiconductor usually causes problemssuch as crystal surface damage, unstable mask at high temperatures, andlateral diffusion under the mask. By forming the GaAs mask layer 22g,these problems are eliminated. Thereafter, part of the top GaAs layer22g was etched away, with the remaining portion being shown in FIG. 2b.Then the structure was sealed in an evacuated quartz tube with ZnAs.sub.2. The Zn diffusion took place at 660° C. for one hour. After thediffusion the GaAs mask layer 22g was etched away with an appropriateetching solution, e.g. H₂ O₂ +NH₄ OH (pH=7.05). Thus, the structureafter the last etching step was similar to that shown in FIG. 2a, exceptfor the contacts 22d and 22e. The structure was then heat treated, atabout 860° C. for 1.5 hours. Following heat treatment, the metalcontacts 22d and 22e were formed.

A scanning electron micrograph of the final structure revealed that theslope of the diffusion front region front is not uniform. The greaterslope in the GaAs layer 22b indicates that the diffusion in GaAs isslower than that in GaAlAs. The PN junction in the GaAs layer 22b is notperpendicular, but rather is tilted. That is, the width of the PNjunction is greater than the thickness of layer 22b. Thus, laser 22 canbe viewed as one being a combination of a heterostructure and ahomostructure. It should however be appreciated that the shape of thejunction may be varied by controlling the diffusion.

The lasing characteristics of the laterally diffused junction laser 22depend strongly on the doping concentration of the N GaAs layer 22b.FIGS. 3a and 3b respectively show the near field and the far field ofthe laser when the doping concentration is low (˜10¹⁷ cm⁻³,Sn doped).The near field has a small tail penetrating into the N side. The farfield shows that the light is not emitted normal to the mirror surface,but at 30° to the N side. This feature can be explained qualitatively asfollows. When the doping concentration of the N GaAs region is muchlower than the Zn diffused P GaAs region, most of the recombination isdue to the hole injection. The gain profile in the N GaAs region isdetermined by the carrier distribution in that region. Because thenumber of holes injected into the N side decays exponetially withdistance, the gain also decays with the distance into the N side.

The laser light generated in the active region is guided along thecavity by a gain profile which decays to one side. Very little light ispresent on the other side because there is very strong absorption in theP type region. The solution of the wave equation in such a medium showsthat the guided modes have wavefronts pointing toward one side, which isthe N side for the case of the laterally diffused junction laser.Consequently, as the laser light exits from the mirror surface, itpropagates to the N side.

When the N type doping concentration of the GaAs layer is increased, thenear field becomes narrower and the peak of the far field moves towardthe center. FIGS. 4a and 4b respectively show the near field and the farfield of the laser 22 with highly doped GaAs layer (˜7×10¹⁸ cm⁻³, Tedoped). The near field is very narrow with half width less than 2 μm.The far field is symmetric and is centered at θ=0° (i.e., is emitted ata right angle to the surface). The laser has single transverse mode andstays stable as the current increases. The difference in the modecharacteristics between lasers with low N doping and high N doping canbe explained qualitatively as due to the fact that at some sufficientlyhigh N doping the increase electron injection into the P type regioncauses the gain-loss profile to become symmetric about the junctionplane and, furthermore, the compensated PN junction region has lowerdoping concentration hence higher index of refraction than those of theregions away from the junction.

The N type dopants used for the GaAs layer 22b is Sn for low doping andTe for high doping. The lasers with the lowest threshold currents havedoping concentration of about 4×10¹⁸ cm⁻³ (Sn doped). FIG. 5 shows themeasured light intensity, curve of one laser as a function of thedriving current. In one embodiment the laser cavity was 300 μm long andthe threshold was 36 mA. No kinks were observed as the current wasincreased up to two times the threshold value. The spectrum of thelasing light was found to change with the N type doping concentration inthe GaAs layer 22b. A number of Fabry-Perot longitudinal modes were seenwhen the doping concentration was low. At concentrations exceeding˜5×10¹⁸ cm⁻³ (obtained by Te doping) a single longitudinal mode wasobserved which is typical of such a laser. FIG. 6 is the spectrum of oneof these lasers. The oscillating wavelength is longer than that oflasers with lower doping concentration, which might be due to the bandtailing at high concentration.

Attention is now directed to FIG. 7 which a three dimensional view ofanother type of a laser 32, fabricated on the semi-insulating GaAssubstrate 15. It consists of five expitaxial layers 32a-32e, which aresuccessively grown on the substrate 15. The five layers are respectivelyGaAlAs of the P type, GaAs which is not intentionally GaAs of the Ptype, GaAlAs of the N type and GaAs of the N type. In one particularembodiment the thickness of layer 32c is about 0.3 μm and those of theconfirming layers 32b and 32d of Ga_(1-X) Al_(X) As where (X˜0.4) are 2μm.

After growing the five layers, an N type metal contact 32f e.g. Au-Ge isevaporated on layer 32e. Then a part of this metal layer 32f is removedphotolithographically. The Au-Ge (as shown in FIG. 7) is used as a maskfor the selective etching of epilayers 32b-32e. The etching is stoppedat the first layer 32a to form a step-like structure (as shown) withedge parallel to the <110> direction. A P-type contact 32g e.g. Au-Zn isthen evaporated on layer 32a. Using the step edge of layers 32b-32f as aself-aligned mask and evaporating the metal Au-Zn at an angle withrespect to the structure, it is possible to separate the P-type andN-type contacts 32f and 32g by a small (˜2 μm) distance. The crystalstructure may then be cleaved to form several lasers of desired lengthse.g. 300 μm. Each laser is preferably mounted on an appropriate heatsink with the leads from both contacts 32f and 32g pointing up.

The laser 32 operates due to current crowding. The current crowdingeffect may be explained as follows. Regarding the edge of the stepstructure or mesa as X=0, when current I flows from the P contact 32g,as it enters the mesa region it splits into two components. Part of it,i(x), flows forward along the first two layers 32a and 32b. Part of itflows upward and across the junction with current density j_(y) (x).Because of the sheet resisitance R of the first two layers the voltagebecomes smaller as x increases. The decreasing rate of the voltage isproportional to the current i(x), i.e., ##EQU1## where R is the sheetresistance of the first two layers and l is the length of the cavity.The derivative of i(x) is proportional to the current which flows acrossthe junction. Therefore, ##EQU2## Taking v=0 at x=0, the junctionequation is written as

    j.sub.y (x)=j.sub.y (0) e.sup.qv(x)/nkT                    (3)

where n is an integer which is 2 near the laser threshold. Substitutingeq. (2) and eq. (3) into eq. (1) one gets ##EQU3## The solution of thisequation is ##EQU4## Substituting eq. (5) into eq. (3) and eq. (1) onegets ##EQU5## Using the condition i (0)=I one gets from eq. (8) ##EQU6##Taking the diffusion length L of the carriers as a characteristiclength, one can rewrite eq. (7) and eq. (10) as ##EQU7## Using α as aparameter i(x) and j_(Y) (x) are plotted in FIGS. 8 and 9 respectively.When α is small or RI is large, the current is crowded more effectivelyto the vicinity of the edge of the step. When α is large or RI is small,the currents spread out further. This current crowding yields a narroweffective gain region near the mesa edge when the diode is driven abovelasing threshold.

Photographs of the near field pattern of the laser 32 at differentcurrents were taken. The picture give direct evidence of the crowdingeffect. With a current 10 mA, way below threshold, indicates a lightdistribution extending a long distance (˜100 μm) under the mesa. Withcurrent above threshold, a much narrower light distribution occurs.Recorded traces of the near field and the far field of the laser areshown in FIG. 10. The half width of the near field is about 5 μm. Thefar field differs from the ordinary far field of a stripe geometry laserby having the peak of the light 10° off to the mesa side with respect tothe normal direction of the mirror surface. A single transverse mode isusually observed when I≦2Ith. Higher order modes appear when the currentis higher. FIG. 11 is a plot of the light intensity as a function of thedriving current. High power operation with linear (no "kink") lightcurrent characteristics is usually achieved. Typical threshold currentof a 300μm long laser is about 150 mA. Differential quantum efficiencyis typically more than 30%.

Although in FIG. 7 the layers 32a and 32b are shown as being of the Ptype and layers 32d and 32e are shown as being of the N type, the typesof these layers may be reversed and the locations of the N type contact32f and the P type contact 32g reversed as well, as shown in FIG. 12,wherein the laser is designated by 32'. It should thus be clear that inlaser 32' the layer 32e which is the first to be grown on the substrate15 is of GaAs of the N type. Both lasers 32 and 32' have similarproperties and characteristics. However, laser 32', due to its GaAs (N)layer 32e being on top of the substrate has an additional, verysignificant advantage. As previously pointed out, GaAs of the N type ischaracterized by high electron mobility. It is for this reason that manyelectron devices such as Gunn oscillators and FET's are fabricated fromGaAs of the N type. Since in laser 32' the bottom layer 32e is of suchmaterial the laser can be easily integrated with any GaAs N type deviceinto a complex monolithic optical device. For the integration purposesthe GaAs N type layer 32e of laser 32' can serve as both the bottomlayer of the laser 32' and the electronic device to be integratedtherewith.

One such integrated arrangement is shown in FIG. 13. The structure tothe left of dashed line 40 represents laser 32', while the structure tothe right of line 40 represents a Gunn device or oscillator 42. Such adevice typically consists of two contacts 42a and 42b on top of a GaAs Ntype layer. As is known, in such a device when the voltage across itscontacts such as 42a and 42b exceeds a selected level the currenttherebetween oscillates. In FIG. 13 the N type contact 32f of the laser32' is shown by dashed lines. This contact is not necessary when thelaser and the Gunn device are integrated, to form the monolithic complexcircuit, since one of the contacts of the Gunn device serves as thelaser's N type contact.

In accordance with the present invention the Gunn device contact 42a,which also serves as the N type contact of the laser. When a voltage isapplied between contacts 32g and 42a, a voltage drop is present betweencontacts 42a and 42b. When this voltage drop is sufficiently high anoscillating current flow is produced. This oscillating current flowsthrough the laser and therefore the laser light beam may be made tooscillate. If the range of the current oscillation is higher than thelaser threshold current, the laser light modulates i.e. varies inintensity. On the other hand, if the threshold current lies in the rangeof the current oscillation the laser light is turned on and offrepeatedly. As is known the frequency of oscillation depends on thedistance between electrodes of the Gunn device and is higher when thedistance is smaller. With an embodiment actually reduced to practicemodulation has been achieved. It should be pointed out that in practicecontacts 42b and 42a should be located close to the mesa, approximatelywhere contact 32f is shown. It is believed that if contact 42a can beplaced sufficiently close to the mesa, contact 42b, to which nopotential is applied may be eliminated.

The integration arrangement, shown in FIG. 13, is not intended to belimited to one in which a laser is integrated with a Gunn oscillator.Other electronic devices may be integrated with the laser on the commonsemi-insulating GaAs substrate. For example a Schottky gate FET may beintegrated. In such a case contact 42a (FIG. 13) may be one of theelectrodes, contact 42b may be used as the gate electrode and the P typecontact 32g on top of the laser, as the third electrode. The FET may beused to modulate the current which drives the laser and therebymodulates light. Since the FET and the laser are integrated on thecommon substrate i.e. made as the same chip very high speed operation ispossible. It should be pointed out that a third FET contact 42c may beadded to provide biasing capabilities. It is apparent that in the FETcontacts 42b and 42c are ohmic contacts and contact 42a is the Schottkycontact.

In FIG. 13 the current crowding effect laser is shown integrated with anelectronic device. Clearly, the invention is not intended to be limitedto such a laser only. If desired the lateral diffusion laser 22, whichwas described in connection with FIG. 2a, may be integrated with theelectronic device. Such an arrangement is shown in FIG. 14, wherein likenumerals are used to designate like elements. It should be pointed outthat in the integrated arrangement, shown in FIG. 13, the N type GaAslayer 32e forms part of the laser 32' and is also the active layer ofthe electronic device 42. In the lateral diffused laser 22 the bottomlayer 22a is of GaAlAs. Thus, to provide the integration the layer 16 ofN type GaAs is first grown on the substrate 15. Only then is the laser22 formed thereon. Layer 16 has excellent lattice matching parameterswith the GaAlAs layer 22a of laser 22. The integrated arrangement ofFIG. 14 has the same advantages as those heretofore described inconnection with FIG. 13.

Although heretofore the various aspects of the invention have beendescribed in connection with GaAs-GaAlAs type devices on asemi-insulating GaAs substrate, the invention is not intended to belimited thereto. Other appropriate materials may be used to form theseparate lasers and or the integrated arrangements on a semi-insulatingsubstrate, formed of other than GaAs. FIG. 15 is a diagram of a lateraldiffused type laser 50 formed on InP semi-insulating substrate 52. Thelaser consists of layers 52a, 52b, and 52c of InP. In GaAsP and InP allof the N type with a P diffused region 52d and P and N contacts 52e and52f. The laser may be integrated with an electronic device 55 withcontacts 55a and 55b above active layer is the InP N type layer 52a.

FIG. 16 shows a similar arrangement in which the laser 60 is of thecrowding effect. It consists of layers 60a, 60b and 60c of InP type N,InGaAlP and InP of the P type and P and N type contacts 60d and 60c. Theelectronic device is designated by 62 and shown having contacts 62a and62b. If the laser 60 is not to be integrated the types of layers 60a and60c may be reversed.

Although particular embodiments of the invention have been described andillustrated herein, it is recognized that modifications and variationsmay readily occur to those skilled in the art, and consequently, it isintended that the claims be interpreted to cover such modifications andequivalents.

What is claimed is:
 1. An arrangement comprising:a GaAs semi-insulatinglayer, representing a substrate with a top surface, a solid state laserstructure on top of said substrate, said laser structure comprisingfirst, second, third, fourth and fifth layers of GaAs N type, a ternarycompound of GaAs of the N type, GaAs, a ternary compound of GaAs P typeand GaAs P type, respectively, above said substrate, with said firstlayer extending beyond the other layers which form a mesa; a firstcontact on top of said fifth layer, a second contact on the top surfaceof said first layer, spaced apart from the other layers which form saidmesa, and electronic means wherein the first GaAs N type layer formspart thereof, said electronic means including an additional contact,with said second contact being adjacent said mesa and the additionalcontact being spaced therefrom in a direction farther away from saidmesa, said electronic means being substantially a Gunn oscillator.
 2. Anarrangement comprising:a GaAs semi-insulating layer, representing asubstrate with a top surface, a solid state laser structure on top ofsaid substrate, said laser structure comprising first, second, third,fourth and fifth layers of GaAs N type, a ternary compound of GaAs ofthe N type, GaAs, a ternary compound of GaAs P type and GaAs P type,respectively, above said substrate, with said first layer extendingbeyond the other layers which form a mesa; a first contact on top ofsaid fifth layer, a second contact on the top surface of said firstlayer, spaced apart from the other layers which form said mesa; and afield effect transistor, definable as FET, beyond said mesa with aSchottky type contact on said first layer, forming the gate electrode ofsaid FET and said second contact being one of the ohmic contacts of saidFET.
 3. An arrangement as recited in claim 2 further including anadditional ohmic contact between said mesa and said Schottky typecontact.
 4. An arrangement comprising:a substrate of semi-insulatingmatter with a resistivity of not less than about 10⁷ ohm-cm a solidstate laser comprising n layers of semi-conductor materials on saidsubstrate, n being an integer, the first of said layers being on saidsubstrate and having lattice matching properties therewith, with therest of said layers extending above said first layer, said layers beingN doped type and including a P doped region, any two adjacent layersbeing respectively of a selective semi-conductor material and a ternarycompound thereof; a first electrical contact on the top surface of thetop layer on the P type region; and a second electrical contact on aportion of said first layer which extends beyond the other layers,wherein said second contact and the portion of the first layer of the Ntype which extends beyond the other layers form part of electronic meansfor controlling the current flow between said first and second contacts,said electronic means comprise a Gunn device.
 5. An arrangement asrecited in claim 4 wherein said Gunn device further includes anadditional contact on said first layer between the other layers and saidsecond contact.
 6. An arrangement comprising:a substrate ofsemi-insulating matter with a resistivity of not less than about 10⁷ohm-cm a solid state laser comprising n layers of semi-conductormaterials on said substrate, n being an integer, the first of saidlayers being on said substrate and having lattice matching propertiestherewith, with the rest of said layers extending above said firstlayer, said layers being N doped type and including a P doped region,any two adjacent layers being respectively of a selective semiconductormaterial and a ternary compound thereof; a first electrical contact onthe top surface of the top layer on the P type region; and a secondelectrical contact on a portion of said first layer which extends beyondthe other layers, wherein said second contact and the portion of thefirst layer of the N type which extends beyond the other layers formpart of electronic means for controlling the current flow between saidfirst and second contacts, said electronic means comprises a fieldeffect transistor, definable as an FET, and further includes a Schottkytype contact on said first layer between said other layers and saidsecond contact.
 7. An arrangement as recited in claim 6 wherein said FETfurther includes an additional contact on said first layer between saidother layers and said Schottky type contact.
 8. In combination with asolid state laser comprising a stack of plurality of layers ofsemi-conductor materials on a semi-insulating substrate with aresistivity of not less than about 10⁷ ohm-cm, the first of said layersbeing N type and extending on said substrate beyond the other layerswith a first electrical contact on the top layer and a second contact onthe first layer, farther removed from the other layers, an arrangementcomprising:at least one additional contact on said first layer whichtogether with the portion of the first layer which extends beyond theother layers form part of an electronic means for controlling thecurrent flow between said first and second contacts.
 9. An arrangementas recited in claim 8 wherein said electronic means in a Gunn device.10. An arrangement as recited in claim 8 wherein said electronic meanscomprises a field effect transistor, definable as an FET, with said atleast one additional contact being a Schottky type contact between saidother layers and said second contact.
 11. An arrangement as recited inclaim 10 wherein said FET includes an additional contact on said firstlayer between said other layers and said Schottky type contact.